Reducing corrosion in plant equipment



it Estates 3,07,223 Patented Feb. 19, 1%63 3,078,223 REDUCENG (IORROSlONIN PLANT EQUHMENT Ralph B. Thompson, Hinsdale, lll., assignor toUniversal Oil Products Company, Des Plaiues, lllL, a corporation ofDelaware N0 Drawing. Filed May 16, 196i Ser. No. 2?,154 9 Claims. (Cl.208-348) This is a continuation-in-part of my copending applicationSerial No. 850,049, filed November 2, 1959, now abandoned, and relatesto a novel method of reducing corrosion in plant equipment. Moreparticularly, the present invention is concerned with reducing corrosioncaused by hot efiiuent products being removed from distillation zones.

In many petroleum refining operations, a petroleum fraction is subjectedto distillation to separate the same into light and heavy products. Thepetroleum fraction generally contains acidic components which result incorrosion of the plant equipment. nents either are present in theoriginal petroleum feed and/or are formed at the high temperatures usedin petroleum conversion reactions. The corrosion is particularly acuteupon cooling of the hot efliuent products withdrawn from a distillationzone.

This corrosion problem is exemplified in the case of a stabilizingcolumn used to strip lighter components from the reaction products of areforming operation. In the reforming operation, a gasoline or naphthais subjected to contact with a reforming catalyst at a temperature offrom about 800 to about 950 F. In the pres ence of hydrogen. Anysuitable reforming catalyst is used and preferably comprises a compositecontaining platinum, more particularly an alumina-platinum composite andstill more particularly an alumina-platinumcombined halogen composite.Other reforming catalysts include composites containing metals orcompounds of metals in the left-hand columns of groups V, Vi and VIII ofthe periodic table. Specific composites in this class arealumina-molybdenum oxide, alumina-molybdenum oxidecobalt oxide,alumina-molybdenum oxide-nickel oxide, aluminum-palladium,alumina-palladium oxide, etc., as Well as the corresponding sulfidesthereof. The charge to reforming may be a full boiling range gasoline ora selected cut thereof, referred to as naphtha and having an initialboiling point within the range of from about 150 to about 350 F. and anend boiling point from about 325 to about 450 F. The reactor effluentproducts are cooled to separate hydrogen for reuse in the process, andthe liquid products are subjected to stabilization to strip lightercomponents therefrom. The lighter components removed as an overhead fromthe stabilizing column contains acidic components, in this caseparticularly HCl, which then are passed through cooling equipment inorder to condense liquid components. The charge to the stabilizercontains water and, upon cooling of the hot efliuent products from thestabilizer, corrosion occurs in the cooling and receiving equipment. Thecooling equipment is generally of the heat exchange type, in which thehot efiluent overhead products from the stabilizer are passed inindirect heat exchange with a heat exchange medium of lower temperature.Considerable difliculty is encountered because of corrosion of the heatexchanger and the resultant necessity of replacing the internalequipment thereof. This in turn necessitates shutting down thestabilizer and, as can be seen, interferes with continuous plantoperation.

Another example of corrosion problems encountered in plant equipment isin the prefractionation of a petroleum charge to separate the same intoa selected fraction or fractions for subsequent catalytic conversion.

These acidic compo- For example, a gasoline fraction may be subjected tofractionation to separate an intermediate or high boiling fraction foruse as charge to a reforming operation of the type hereinb-eforedescribed. The fraction subjected to such separation contains acidiccomponents and water and, upon cooling of the overhead products,corrosion of the cooling and receiving equipment occurs. This problem isacute and, as mentioned above, it results in too frequent shut-downs toreplace the internals of the heat exchanger type coolers, the connectingpiping and/ or receiver, and necessitates discontinuing theprefractionator operation.

The above are two examples in which serious corrosion problems areencountered upon cooling of the hot effluent products of a distillationzone. The term distillation zone is used in the generic sense to includeany type of fractionation, stripping, stabilization, etc. in which theoverhead effluent products are subjected to cooling to separate acondenstae. In most cases a portion of the condensate is recycled to theupper portion of the distillation zone as a cooling and refluxing mediumtherein.

In the operation of the distillation zone of the class hereinbeforedescribed, it is important that the pH of the overhead be controlled.For best operations, the pH should be within the limits of from about 5to about 7 and still more particularly from about 6 to about 6.8. Onemethod of controlling the pH is to introduce an inorganic alkaline agentinto the overhead eflluent products. Suitable inorganic alkaline agentsinclude sodium compounds such as sodium hydroxide, sodium carbonate,disodium phosphate, trisodium phosphate, etc. or mixtures thereof. Otheralkaline agents include the corresponding potassium compounds, lithiumcompounds, rubidium compounds, ammonium hydroxide, etc. or mixtures ofone or more of these with the sodium compounds. These alkaline agentspreferably are prepared as aqueous solutions and are injected into thehot eflluent products leaving the distillation zone. It also isnecessary to utilize a corrosion inhibitor and, for practical purposes,it is desirable to form a single solution of both the inorganic alkalineagent and the corrosion inhibitor, and to inject this combined solutioninto the hot efiiuent products. This avoids the necessity of utilizingseparate pumping equipment which otherwise would be required in the caseof a non-Water soluble corrosion inhibitor.

A water soluble corrosion inhibitor offers a number of advantages. Inthe first place, it will penetrate the aqueous phase and thereby serveto protect the inner surfaces of the piping and heat exchange equipmentthrough which the hot er'lluent products pass. Secondly, the watersoluble corrosion inhibitor will settle out in the water phase in asubsequent settler or receiver and thereby be withdrawn from theprocess. As another advantage, the water soluble corrosion inhibitor maybe prepared as a solution in water which obviously is the leastexpensive solvent available. As hereinbefore set forth, the aqueoussolution is prepared to contain both the alkaline agent and thecorrosion inhibitor and this offers the improtant advantage ofpermitting simultaneous introduction of both of these materials in asingle step.

While the water soluble corrosion inhibitor offers the advantages setforth above, the corrosion inhibitor must meet several stringentrequirements. in the first place, the inhibitor must be Water solubleand remain in solution in the aqueous menstruum. Secondly, the corrosioninhibitor must not cause emulsification problems which will interferewith the subsequent separation in the settler or receiver of a waterphase from a petroleum phase. In addition, the corrosion inhibitor mustbe reasonable in cost in order to justify its use.

The present invention is based on discovery that an effective watersoluble corrosion inhibitor may be prepared from certain by-productchemicals which are available commercially at a lower cost than purechemicals. Surprisingly, it has been found that these lower cost, lesshighly refined and mixed by-product materials may be used in preparingeffective water soluble corrosion inhibitors which meet the requirementshereinbefore set forth. Normally it would be expected that the use ofthese by-product materials would not satisfy the stringent requirementshereinbefore set forth and that substantially pure chemicals would berequired for the preparation of satisfactory corrosion inhibitors. Aswill be shown in the appended examples, almost the reverse is truebecause a corrosion inhibitor prepared from a substantially purechemical instead of the by-product material resulted in a highly gelledproduct which was ditlicultly soluble in water. As will be hereinafterset forth in detail, the water soluble inhibitor for use in the presentinvention is prepared by the partial esterification of the condensationproduct of alkylene oxide with a polyamine residue. The use of thepolyamine residue surprisingly offers advantages in the preparation ofthe inhibitor as set forth above. However, it also is an important andessential feature of the present invention that the esterification ofthe oxyalkylated polyamine residue is a partial esterification only andis effected using a critical mole ratio of acid to oxyalkylatedpolyamine residue. As will be shown by the examples appended to thepresent specifications, esterification in excess of the critical rangeherein specified results in an inhibitor which is not water soluble andtherefore cannot be used for the purposes herein set forth.

In one embodiment the present invention relates to the method ofreducing corrosion of plant equipment upon cooling of hot effluentproducts from a distillation zone and avoiding emulsification duringsubsequent separation, which comprises incorporating in said hotefiluent products an inorganic alkaline agent and a water solubleinhibitor prepared by (1) condensing an alkylene oxide with a highboiling polyamine residue under conditions to replace each aminehydrogen of said polyamine residue with an oxyaikylene group, saidresidue remaining after distilling off lighter products formed in themanufacture of ethylene diamine, and (2) thereafter partiallyesterifying the resultant condensation product by reacting with not morethan about 0.25 mole per mole of the oxyalkylated polyamine residue of amixed carboxylic acid containing from about 16 to about 40 carbon atomsper molecule, and subsequently cooling said hot effluent products.

In a specific embodiment the present invention relates to a method ofreducing corrosion of heat exchanger equipment during the cooling of hotoverhead effluent products containing HCl from a hydrocarbonstabilization zone and avoiding emulsification during subsequentseparation of aqueous and hydrocarbon phases which comprisesincorporating in said hot overhead effiuent products, prior to coolingthereof, an aqueous solution of both a sodium compound in aconcentration to maintain a pH of from about 6 to about 6.8 in saideffluent products and a water soluble corrosion inhibitor prepared by(1) condensing ethylene oxide with a high boiling polyamine residueunder conditions to replace each amine hydrogen of said polyamineresidue with an oxyethylene group, said residue remaining afterdistilling off tetraethylenepentamine and lighter products formed in themanufacture of ethylene diamine by the reaction of ethylene chloride andammonia, and (2) thereafter partially esterifying the resultantcondensation product by reaction with tall oil acid in a mole ratio ofacid to oxyethylated polyamine residue of from about 0.1 to about 0.25:1, subsequently cooling said hot efiiuent products and there- 4 afterseparating an aqueous phase from a hydrocarbon phase.

As hereinbefore set forth and as will be shown in the appended examples,it is an important and essential feature of the present invention thatthe esterification of the oxyalkylated polyamine residue be effectedusing not more than about 0.25 mole of acid per mole of polyamineresidue, and more particularly from about 0.1 to about 0.25:1 mole. Theuse of larger concentrations of acid results in products which are notwater soluble and therefore will not offer the advantages of the watersoluble inhibitor as previously described. The use of lesserconcentrations of acid, on the other hand, will not produce the improvedcorrosion inhibitors.

In addition to the important requirement of critical mole ratio of acidand amine, it has been found that effective water soluble corrosioninhibitors are prepared through the use of lay-product chemicals. Theby-product chemical used as the amine portion and reactant in thepreparation of the corrosion inhibitor of the present invention is thepolyamine residue remaining after distilling off lighter products in themanufacture of ethylene diamine. Ethylene diamine is prepared byreacting ethylene chloride with ammonia. During the reaction, productsboiling above ethylene diamine are inherently produced. In the recoveryof the products from the ethylene diamine manufacture, ethylene diamine,diethylene triamine, triethylene tetramine and tetraethylene pentamineare distilled off and further separated to recover the individualpolyamines as substantially pure chemical products. Remaining higherboiling products are recovered as a residue and, as hereinbefore setforth, it has been found that this residue is particularly suitable andapparently unique for use in preparing the corrosion inhibitor of thepresent invention. This polyamine residue is available commercially froma number of sources. One example is Amine E400 sold by the Dow ChemicalCompany. This polyamine residue has a specific gravity at 77/77 F. of0.956-0962 and a boiling range at 760 mm. of 5% at 381 F. and at 80% of437 F. A similar polyamine residue is available from Carbide & Carbon asPolyamine H Special. In some cases a lighter polyalkylene-polyamine,particularly diethylene triamine and/or triethylene tetramine, isblended with the polyamine residue in small amounts, say from about 1%to about 15% by weight, in order to reduce the viscosity and tofacilitate pumping and handling thereof. This may serve to increase thespecific gravity at 77/ 77 F. to an upper limit of about 0.999 orslightly higher.

The polyamine residue has a high basic nitrogen and accordingly morereserve alkalinity. Apparently this is one of the important propertiesof the polyamine residue which makes it particularly effective for usein preparing the corrosion inhibitor of the present invention. It isapparent that the polyamine residue is a complex mixture of polyaminesand accordingly may vary in its specific composition. It has been foundthat the polyamine residue contains heterocyclic amine compoundsincluding, for example, derivatives of poly-aminoethyl piperazines.

While the polyamine residue is peculiarly suitable fo use as a reactantin preparing the corrosion inhibitor of the present invention, thepolyamine residue must be further reacted in a specific manner toprepare the corrosion inhibitor. Accordingly, the polyamine residue isreacted with an alkyleue oxide containing from 2 to 4 carbon atoms, andparticularly ethylene oxide, under conditions to replace each of theamino hydrogens with an oxy-ethylene group. This is an importantrequirement in order that the inhibitor product meets the requirementshereinbefore set forth. This is readily accomplished by reacting thepolyamine residue with the alkylene oxide at a temperature of from aboutto about 300 F. and preferably from about to about F. in the presence offrom about 5% to about 30% by weight of Water based upon the polyamineresidue. Furthermore, the reaction is effected in the absance of acatalyst, as this has been found to limit the substitution of only onealkylene oxide group for each amino hydrogen. Accordingly, the alkyleneoxide is reacted in a stoichiometric equivalent to the amino hydrogensof the polyamine residue. Generally an excess of alkylene oxide is usedin order to insure complete reaction of all amino hydrogens. Ashereinbefore set forth, in the absence of a catalyst, the substitutionof the amino hydrogens will be limited to one alkylene oxide group peramino hydrogen. The reaction is effected readily by gradually adding thealkylene oxide to a heated and stirred mixture of the polyamine residue.The product is a black viscous liquid and in a preferred embodiment thewater previously added is not removed and the intermediate productcontaining Water then is further reacted in a manner to be hereinafterdescribed. If advantages appear therefor, it is understood that thewater may be removed but, as hereinbefore set forth, it generally ispreferred to allow the water to remain.

As hereinbefore set forth, ethylene oxide is preferred for use inreacting with the polyamine residue. In a broad embodiment, the a kyleneoxide contains from 2 to 4 carbon atoms and thus includes propyleneoxide and butylene oxide. Butylene oxide, when employed, preferably is amixture of straight chain isomers as present in the butylene oxidemixture commercially available.

As hereinbefore set forth, the novel corrosion inhibitor of the presentinvention is prepared from low cost mixed chemicals. A preferred mixedchemical used in the next step of the process is tall oil acid which isa mixture of saturated and unsaturated fatty acids, rosin acid and alsocontains non-acidic materials such as esters, lactones, estclides,alcohols such as sterols, etc. This mixture is obtained by acidifyingthe black liquor skimmings formed in the pulping of wood, usually pine,by the sulfate (kraft) process. The black liquor produced during thepulping of wood is partially concentrated, then settled and the curdysoap skimmed from the top of the settling liquor. The skimmings areacidified with sulfuric acid (usually of 50 to 98% concentration) andthe mixiture heated to about 100 C., followed by decantation of theliberated tall oil. The manufacture, purification, composition, etc., oftall oil is described in Encyclopedia of Chemical Technology, volume 13,pages 572-7 (1954).

The crude tall oil may contain a mixture of unsaturated fatty acids suchas oleic, lineoleic, lineolenic, and the like, rosin acids, all of whichhave not been identified, but some of which are of the abietic type orthe pimaric type, alcohols such as sterol, esters of alcohols with thefatty acids and the rosin acids, lactones, hydrocarbons, and compoundswhich have not as yet been identified. During purification of the talloil by many of the usual processes such as treatment with mineral acid,distillation under reduced pressure, solvent extraction, or othermethods, a series of chemical reactions may occur among the tall oilconstituents so as to modify further the composition of tall oil.

Either the crude tall oil acid or purified tall oil acid may be used.The properties of five commercial tall oil acids are shown in theEncyclopedia of Chemical Technology reference mentioned above.

In a preferred embodiment of the invention, the tall oil acid is low inrosin acid content. One commercially available tall oil acid isavailable commercially as Indusoil L-S and is said to have an acidnumber of 183-196, a saponification number of 190-198, a fatty acidcontent of 90% minimum, a rosin acid content of 5% maximum and aspecific gravity at 60/60 F. of 0.905- 0910. Another tall oil acid isavailable commercially as Crofatol No. l and is said to have an acidnumber of 192 minimum, an iodine value of l25135 and a rosin acidcontent of 1.5% maximum. Still another tall oil acid was Aliphant 44-and was said to have an acid value of 192198, an iodine value of125-135, a rosin acid content of 1.5% maximum. The acid composition wassaid to be composed of 50% oleic acid, 46% linoleic acid, 2% palmiticacid, 1% stearic acid and 1% rosin acid. Here again it is noted that themixed chemical may vary in its composition, but will contain 18 carbonatom fatty acids in a major concentration.

Another mixed by-product acid which may be used in accordance with thepresent invention is marketed commercially under the trade name of VR1Acid. This is an acid residue produced by distilling, at about 270 C.under about 4 mm. of mercury pressure, the byproduct acids obtained inthe preparation of sebacic acid by fusing castor oil with alkali.Production of this residue is described in more detail in U.S. Patent2,267,- 269 to Cheetham et al. In the manufacture of sebacic acid fromcastor oil, the oil is heated with a caustic alkali. This splits theoil, forming octanol2, methyl hexyl ketone, the alkali salt of sebacicacid, and the alkali salts of various other long-chained acids. Thealcohol and ketone are readily removed from the reaction mixture bydistillation. The alkali salts which remains then are dissolved in waterand, upon slight acidification of the resulting solution, an oily layerseparates. At a pH of about 6, the aqueous phase contains the alkalisalt of sebacic acid, while the oily layer contains various other acidsfrom the reaction. The term by-product acids is generally applied to themixture of acids forming the oily layer.

These by-product acids then are separated into two parts. After theseacids have been washed with a dilute mineral acid, such as sulfuric orhydrochloric, they are washed with water and dried. They then aredistilled under reduced pressure. Fatty acids which are primarilymonobasic carboxylic acids are taken off at 100 C. to 270 C. atpressures as low as 4 mm. This treatment leaves a residue which is amixture of fatty acids, apparently primarily polybasic in character andincluding 36 carbon atoms per molecule acids. The residue iscommercially available from Rohm & Haas Company under the trade name ofV1 1 Acid and has an average molecular weight of 500600, an acid numberof 134- 160, a saponiiication number of 174179, an an iodine number of5360. A similar product sold by Wallace & Tiernan is D50 Acid.

Still another mixed by-product acid is being marketed commercially underthe trade name of Dimer Acid. Still another preferred acid is marketedcommercially under the trade name of Empol 1022. This dimer acid is adiiinoleic acid (36 carbon atoms per molecule) and is a represented bythe following general formula:

This acid is a viscous liquid, having an apparent molecular weight ofapproximately 600. It has an acid value of 180192, an iodine value of 5,a saponification value of l'195, a neutralization equivalent of 290-310,a refractive index at 25 C. of 1.4919, a specific gravity at 15.5C./15.5 C. of 0.95, a flash point of 530 F., a fire point of 600 F, anda viscosity at C. of 100 centistokes.

For economic reasons, it is apparent that the use of the mixedby-product acids offers advantages. It is under stood that othersuitable mixed acids may be employed including, for example, crude oleicacids, referred to in the trade as red oil, etc. in addition to theeconomic advantage, the mixed acid also offer the advantage of producinga lower melting product and therefore improves the fluidity at lowertemperatures. These mixed acids will comprise carboxylic acids havingfrom about 16 to about 40 carbon atoms per molecule. The tall oils, forexample, comprise principally acids containing 18 carbon atoms permolecule, but also may contain some lighter and heavier acids. The VR-land similar acids will comprise principally acids having 36 carbon atomsper molecule, but here again will contain some lighter and heavier acid.These mixed acids are being defined as containing from about 16 to about40 carbon atoms per molecule and more particularly from about 18 toabout 36 carbon atoms per molecule.

The mixed acid is reacted with the oxyalkylated polyamine residueprepared as hereinbefore set forth to form the corrosion inhibitor ofthe present invention.

As hereinbefore set forth, it is essential that the proportion of acidand oxyalkylated polyamine residue is within the critical rangeshereinbefore set forth. This reaction is effected in the absence of acatalyst by heating and stirring the mixture of the oxyalkylatedpolyamine residue and tall oil acid, for example, at a temperature offrom about 215 to about 320 F. In general, this temperature should notbe surpassed because excessive temperature produces side reactions andresults in a prodnot of undesirable properties. Water originally presentin the reactants and that formed during the esterification reaction arecontinuously removed during the heating and reacting. The time ofreaction may range from about 1 /2 to about 8 hours, after which thereaction product is allowed to cool and is recovered as a black viscousliquid.

While the water soluble corrosion inhibitor prepared in the above mannermay be utilized as such, in a preferred embodiment it is prepared as anaqueous solution and, as hereinbefore set forth, is commingled with thealkaline agent. In one embodiment the solution contains from 30% to 70%by Weight of active ingredient and the balance is solvent. In manycases, it is desirable to include an alcohol as part of the solvent andaccordingly the solvent may comprise from about 10% to about 50% alcoholsuch as ethyl alcohol, isopropyl alcohol, butyl alcohol, etc. and thebalance is water.

As hereinbefore set forth, in a preferred embodiment the alkaline agentis commingled with the corrosion inhibitor to form a mixed solution forsingle injection. The specific amount of alkaline agent and corrosion inhibitor to be used will depend upon the degree of acidity of theoverhead effluent products. A suitable mixture was prepared to contain500 grams of trisodium phosphate per pint of inhibitor solutioncontaining 50% by Weight of corosion inhibitor and a solvent consistingof isopropyl alcohol and Water. It is apparent that additional water isused to make a free flowing stable solution. The amount of water is notcritical because the water is subsequently separated from thehydrocarbon constituents of the overhead eflluent products. Accordingly,excess water is readily removed from the process. In one method, thesolution of corrosion inhibitor and alkaline agent are put in a suitablevessel and sufficient water commingled therewith to form the desiredsolution. In the example of one pint of corrosion inhibitor (50% activeingredient) and 500 grams of trisodium phosphate, about 5 or 6 gallonsof water are used to form the final solution.

As hereinbefore set forth, the amount of corrosion inhibitor used varieswith the acidity of the overhead efiluent products. In general, thecorrosion inhibitor, based on active ingredient, is used in aconcentration of from about 0.00001% to about 0.01% by weight of theoverhead efiluent products and preferably from about 0.0001% to about0.001% by weight. The alkaline agent is used in an amount to control thepH of the overhead eifiuent products from about 5.0 to about 7.0 andpreferably from about 6.0 to about 6.8.

The following examples are introduced to illustrate further the noveltyand utility of the present invention but I not with the intention ofunduly limiting the same.

8 EXAMPLE I 368 grams of polyamine residue (Amine E-) and 60 grams ofwater were stirred in a B-necked flask while held in a Water bath at atemperature of about F. 319 grams of ethylene oxide were graduallyintroduced into the reaction flask. The reaction was mildly exothermic.Heating and stirring of the reactant were continued while thetemperature was held at about F.

The oxyethylated polyamine residue prepared in substantially the samemanner as described above was reacted with tall oil acid (Aliphat 44-A).73.5 grams of the oxyethylated polyamine residue were mixed with 30grams of the tall oil acid and the mixture heated in an oil bath untilthe flask reached a temperature of 320 F. The flask was open at the topso that the water originally introduced and formed in the reaction wasallowed to escape. The product was recovered as a black viscous liquid.

Solutions of the products formed in the above manner were prepared tocontain one gram of the corrosion inhibitor, two grams of sodiumhydroxide and 250 cc. of water. The solution remained clear afterstanding for 24 days at room temperature.

EXAMPLE II Oxyethylated polyamine residue was prepared in substantiallythe same manner as described in Example I, except that the polyamineresidue used in this example is Polyamine H Special, which is similar inproperties to the Amine E-lOO described in Example I and previously inthe specifications. A number of separate esterification products wereprepared by reacting the oxyethylated polyamine residue with tall oilacid (Indusoil L-S). In these preparations the mole proportion of acidto oxyethylated amine residue was varied as shown in the followingtable:

Table I Oxyethylated Preparation No. Polvamine Acid M le Ratio Residue(Grams) Acid: Amino (Grams) 30. 8 45 0. 422: 1 3S. 8 30 O. 253:1 73. 530 0. l4 :1

Preparation A was insoluble in water. It will be noted that the moleratio of acid to amine is above the critical upper limit of 0.25 acid toamine mole ratio hereinbefore set forth.

Preparation B was a very viscous material and there fore not desirablefor use in accordance with the present invention.

Preparation C was completely soluble in water. It will be noted that theratio of acid to amine is within the desired range of 0.1 to 0.25heretofore set forth.

EXAMPLE III Additional compositions similar to those described inExample II are prepared to comprise effective corrosion inhibitors whichare water soluble and accordingly are comprised within the presentinvention.

Table II oxyethylated Preparation N o. Polyamine Acid Mole Ratio vResidue (Grams) Acid: Amine (Grams) 9 EXAMPLE IV The inhibitor asprepared in the manner described in Example I was evaluated as acorrosion inhibitor in the following manner: In this test a steel metalcoupon of about A" x 6" x is suspended in the vapor space of a one literflask containing 300 cc. of a heptane fraction and 50 cc. of corrosivewater having a pH of 1.5, the flask being equipped with a refluxcondenser at the top. Hydrogen sulfide is continuously introduced intothe lower portion of the flask. The flask is maintained at a temperatureof 212 F. and the rising vapors pass over the test coupon, are collectedat the top of the flask and the condensate passes downward over the testcoupon. A continuous stream' of Water cornmingles with the condensateand passes over the test coupon. The test is continued for 16 hours,after which the loss in Weight due to corrosion is determined byweighing.

The following table reports the results of a run in the absence of acorrosion inhibitor and two runs in which an inhibitor prepared asdescribed in Example I is added to the water which passes over the testcoupon. In one case, the inhibitor was added in a concentration of 0.1%by weight of the Water and in the other case in a concentration of 0.05%by weight of the water.

From the data in the above table, it will be noted that the corrosionwas reduced considerably in the samples containing the inhibitor of thepresent invention.

EXAMPLE V As hereinbefore set forth, it is important that the corrosioninhibitor does not cause emulsification and thereby interfere with theseparation of the hydrocarbon and aqueous phases in the receiver. Theemulsification Was evaluated in the following manner: In a 50 ml.volumetric flask, 50 mg. of the corrosion inhibitor is dissolved tovolume with Water. The desired amount of corrosion inhibitor is removedby pipetting and is diluted with water to give 100 grams of solution.For example, 2 ml. of the above solution will give a concentration of 20parts per million in 100 grams of water. 30 ml. from the 100 grams ofsolution are poured into a glass stoppered 100 cc. graduate. 70 ml. of aheptane fraction is added. The graduate is shaken vigorously for 2minutes and then allowed to stand for minutes. The amount of emulsion atthe interface is noted.

When evaluated in the above manner, the interface was very clean andshowed no emulsion.

EXAMPLE VI Another corrosion inhibitor was prepared in substantially thesame manner described in Example I except that the tall oil acid waslndusoil L-S. The properties of this acid have been hereinbefore setforth. The product was recovered as a black viscous liquid and wasprepared as a 50% solution of active ingredient in a solvent consistingof 40% isopropyl alcohol and 60% water. The properties of the solutionare as follows:

Specific gravity at 60 F 1.0095 Kinematic viscosity at 100 F cst 43.38Universal viscosity at 100 F secs 201.7 Tag open cup flash point F 84 i0EXAMPLE vn As hereinbefore set forth, it is essential that the polyamineresidue be reacted with alkylene oxide prior to esterification with thetall oil acid. An additive was prepared by reacting the polyamineresidue (Amine El00) and tall oil acid but the product was a gel andcould not be readily handled. The solubility in water was notsatisfactory.

EXAMPLE VH1 Another additive was prepared in the manner described inExample VI except that tetraethylene pentamine was used instead of thepolyamine residue. When evaluated in the emulsification test describedin Example IV, the emulsification tendency was rated at 1 ml. at theinterface. In contrast to this, the inhibitor prepared according toExample I was rated at less than 0.5 and was reported as very clean.

EXAMPLE IX Another corrosion inhibitor was prepared substantially in thesame manner as Example I except that VR-l Acid was used in theesterification step. When evaluated in the same manner as described inExample IV, 0.05% by Weight of the inhibitor served to reduce the weightloss from 25.6 mg. to 7.7 mg. Here again it will be noted that theinhibitor serves to considerably reduce corrosion of the metal coupon.

EXAMPLE X As hereinbefore set forth, a particular advantage of the watersoluble corrosion inhibitors of the present invention is that they maybe prepared as a combined solution with alkaline agents. A 50 percent byweight active ingredient solution of the inhibitor prepared as describedin Example I in a solvent consisting of 70% water and 30% isopropylalcohol was prepared. One pint of this solution and 500 grams oftrisodium phosphate were placed in a 6 gallon drum and additional waterwas added thereto to fill the drum. About one-half of the resultantsolution was added per day to the hot overhead efiiuent products of aprefractionator used to separate a naphtha into an overhead fraction,having an end boiling point of about 200 F, and a heavier fraction foruse as charge to a reforming operation. The charge rate is about 1400barrels per day and the prefractionator is maintained at a pressure ofabout 40 pounds per square inch with a bottoms temperature of about 400F. and a top temperature of about 200 F.

The charge to the prer'ractionator is saturated with water and alsocontains HCl. This resulted in excessive corrosion of the coolers usedto condense the overhead products from the prefractionator. Corrosion ofthis equipment is reduced by injecting the combined solution oftris-odium phosphate and corrosion inhibitor into the overhead productsprior to cooling thereof, thereby considerably increasing the life ofthis equipment.

EXAMPLE XI The naphtha charge separated as a bottoms product in theprefractionator described in Example 1X is subjected to reforming in thepresence of an alumina-platinun1-combined halogen catalyst and hydrogenat a temperature of about 900 F. The reactor effluent products arecondensed to separate hydrogen for recycle from liquid, the liquid beingsubjected to stabilization to strip out lighter components. Thestabilizer is operated at a pressure of about 300 pounds, utilizing atemperature at the bottom of 425 F. and at the top of about F. The hotoverhead efiluent products are cooled and collected in a receiver,wherefrom normally gaseous components are separated from condensate. AWater layer collects at the bottom of the receiver and is separatelywithdrawn.

Considerable corrosion was encountered in such an operation and this wasfollowed by analyzing the iron and copper content, as well as the pH, ofthe water being withdrawn from the receiver. In one operation in whichno additive was incorporated in the overhead eiiiuent products, the pHof the water sample was 4.1 and it contained 93.6 parts per million ofiron and 5.5 parts per million of copper. About one-half of thecorrosion inhibitoratrisodium phosphate solution prepared as describedin Example 1X was injected daily into the overhead efiiuent productsprior to cooling. This served to increase the pH of the overheadproducts, as determined by analysis of the water withdrawn from thereceiver, to between 6.2 and 6.8 and to reduce the iron to as low as 1.6parts per million and the copper to as low as 0.6 part per million. Itmust be appreciated that the acidity of the charge to the stabilizercontinuously changes and accordingly the pH of the overhead efiiuentproducts and the iron and copper concentrations of the water fluctuate.However, it will be noted that there was a considerable reduction in thecorrosion of the cooling and receiving equipment through which theoverhead efiiuent products pass.

I claim as my invention:

1. A method of reducing corrosion of plant equipment upon cooling of hotefiluent products from a distillation zone and avoiding emulsificationduring subsequent separation, which comprises incorporating in said hoteffluent products a mixed solution of an inorganic alkaline agent and awater soluble corrosion inhibitor prepared by (l) condensing an alkyleneoxide containing from 2 to 4 carbon atoms with a high boiling polyamineresidue under conditions to replace each amine hydrogen of saidpolyamine residue with an oxyalkylene group, said residue being theresidual material remaining after distilling off tetraethylene pentamineand lighter products formed in the manufacture of ethylene diamine bythe reaction of ethylene chloride with ammonia, and (2) thereafterpartially esterifying the resultant condensation product by reactingwith a mixed carboxylic acid containing from about 16 to about 40 carbonatoms per molecule in a mole ratio of acid to oxyalkylated polyarnineresidue of from about 0.1 to about 0.25:1, and subsequently cooling saidhot efiiuent products.

2. A method of reducing corrosion of cooling and receiving equipmentthrough which hot eflluent products from a distillation zone pass andavoiding emulsification during separation, which comprises incorporatingin said hot eflluent products a mixed solution of an inorganic alkalineagent and a water soluble corrosion inhibitor prepared by (1) condensingethylene oxide with a high boiling polyamine residue under conditions toreplace each amine hydrogen of said polyamine residue with anoxyethylene group, said residue being the residual material remainingafter distilling oif tetraethylene pentamine and lighter products formedin the manufacture of ethylene diamine by the reaction of ethylenechloride with ammonia and (2) thereafter partially esteritying theresultant condensation product by reacting with tall oil acid in a moleratio of acid to oxyethylated polyamine residue of from about 0.1 toabout 0.25:1, and subsequently cooling said hot efiluent products.

. 3. A method of reducing corrosion of cooling and receiving equipmentthrough which hot efiluent products from a distillation zone pass andavoiding emulsification during separation, which comprises incorporatingin said hot efiiuent products a mixed solution of an inorganic alkalineagent and a water soluble corrosion inhibitor prepared by (1) condensingethylene oxide with a high boiling polyamine residue under conditions toreplace each amine hydrogen of said polyamine residue with anoxyethylene group, said residue being the residual material remainingafter distilling ofi tetraethylene pentamine and lighter products formedin the manufacture of ethylene diamine by the reaction of ethylenechloride with ammonia, and (2) thereafter partially esterifying theresultant condensation product by reacting with a dicarboxylic acidcontaining 36 carbon atoms per molecule in a mole ratio of acid tooxyethylated polyamine residue of from about 0.1 to about 0.25 :1, andsubsequently cooling said hot eflluent products.

4. A method of reducing corrosion of cooling and receiving equipmentupon cooling of overhead effluent products from a distillation zone andavoiding emulsification during subsequent separation, which comprisesincorporating in said effluent products prior to cooling thereof a mixedaqueous solution of both a sodium compound and a water soluble corrosioninhibitor prepared by (1) condensing ethylene oxide with a high boilingpolyamine residue under conditions to replace each amine hydrogen ofsaid p-olyamine residue with an oxye'thylene group, said residue beingthe residual material remaining after distilling cit tetraethylenepentamine and lighter products formed in the manufacture of ethylenediamine by the reaction of ethylene chloride ammonia, and (2) thereafterpartially esterifying the resultant condensation product by reactingwith tall oil acid in a mole ratio of acid to oxyethylated polyamineresidue of from about 0.1 to about 0.25:1, and subsequently cooling saidhot efiiuent products.

5. The method of claim 4 further characterized in that said sodiumcompound is sodium hydroxide.

6. The method of claim 4 further characterized in that said sodiumcompound is trisodium phosphate.

7. The method of claim 4 further characterized in that said distillationzone is a prefractionator to separate light components from a naphthacharge for catalytic reforming.

8. The method of claim 4 further characterized in that said distillationzone in a stabilizer used to strip light components from the efliuentproducts of a reforming operation.

9. The method of claim 4 further characterized in that said sodiumcompound is introduced in a concentration to maintain the pH of saideffluent products within the range of 6.0 to 6.8.

References Qited in the file of this patent UNITED STATES PATENTS2,218,495 Balcar Oct. 15, 1940 2,408,011 \Nalsh et al Sept. 24, 19462,854,323 Shen Sept. 30, 1958 2,854,324 Shen Sept. 30, 1958 2,883,277Beiswanger et al. Apr. 21, 1959 3,003,955 Jones Oct. 10, 1961 V FOREIGNPATENTS 533,564 Canada Nov. 20, 1956

1. A METHOD OF REDUCING CORROSION OF PLANT EQUIPMENT UPON COOLING OF HOTEFFLUENT PRODUCTS FROM A DISTILLATION ZONE AND AVOIDING EMULSIFICATIONDURING SUBSEQUENT SEPARATION, WHICH COMPRISES INCORPORATING IN SAID HOTEFFLUENT PRODUCTS A MIXED SOLUTION OF AN INORGANIC ALKALINE AGENT AND AWATER SOLUBLE CORROSION INHIBITOR PREPARED BY (1) CONDENSING AN ALKYLENEOXIDE CONTAINING FROM 2 TO 4 CARBON ATOMS WITH A HIGH BOILING POLYAMINERESIDUE UNDER CONDITIONS TO REPLACE EACH AMINE HYDROGEN OF SAIDPOLYAMINE RESIDUE WITH AN OXYALKYLENE GROUP, SAID RESIDUE BEING THERESIDUAL MATERIAL REMAINING AFTER DISTILLING OFF TETRAETHYLENE PENTAMINEAND LIGHTER PRODUCTS FORMED IN THE MANUFACTURE OF ETHYLENE DIAMINE BYTHE REACTION OF ETHYLENE CHLORIDE WITH AMMONIA, AND (2) THEREAFTERPARTIALLY ESTERIFYING THE RESULTANT CONDENSATION PRODUCT BY REACTINGWITH A MIXED CARBOXYLIC ACID CONTAINING FROM ABOUT 16 TO 40 CARBON ATOMSPER MOLECULE IN A MOLE RATIO OF ACID TO OXYALKYLATED POLYAMINE RESIDUEOF FROM ABOUT 0.1 TO ABOUT 1.25:1, AND SUBSEQUENTLY COOLING SAID HOTEFFLUENT PRODUCTS.